Re: multivariate statistics (v19)

From: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
To: Dilip Kumar <dilipbalaut(at)gmail(dot)com>
Cc: Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tatsuo Ishii <ishii(at)postgresql(dot)org>, David Steele <david(at)pgmasters(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Álvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Petr Jelinek <petr(at)2ndquadrant(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: multivariate statistics (v19)
Date: 2017-01-03 16:22:48
Message-ID: 7c4b2088-5cbd-dfec-0b98-16e5a7db5308@2ndquadrant.com
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On 01/03/2017 02:42 PM, Dilip Kumar wrote:
> On Tue, Dec 13, 2016 at 3:20 AM, Tomas Vondra
> <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>> attached is v21 of the patch series, rebased to current master (resolving
>> the duplicate OID and a few trivial merge conflicts), and also fixing some
>> of the issues you reported.
>
> I wanted to test the grouping estimation behaviour with TPCH, While
> testing I found some crash so I thought of reporting it.
>
> My setup detail:
> TPCH scale factor : 5
> Applied all the patch for 21 series, and ran below queries.
>
> postgres=# analyze part;
> ANALYZE
> postgres=# CREATE STATISTICS s2 WITH (ndistinct) on (p_brand, p_type,
> p_size) from part;
> CREATE STATISTICS
> postgres=# analyze part;
> server closed the connection unexpectedly
> This probably means the server terminated abnormally
> before or while processing the request.
> The connection to the server was lost. Attempting reset: Failed.
>
> I think it should be easily reproducible, in case it's not I can send
> call stack or core dump.
>

Thanks for the report. It was trivial to reproduce and it turned out to
be a fairly simple bug. Will send a new version of the patch soon.

regards

--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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